Tris (2,2′-bipyridyl)ruthenium(II) Electrogenerated Chemiluminescence in Analytical Science

Abstract

Ru(bpy)2+3 electrogenerated chemiluminescence (CL) has rapidly gained importance as a sensitive and selective detection method in analytical science. The Ru(bpy)2+3 ECL is observed when Ru(bpy)3+3 reacts with Ru(bpy)+3 and yields an excited state Ru(bpy)2+3*. ECL emission can also be obtained when a variety of oxidants and reductants react with the reduced or oxidized forms of Ru(bpy)2+3. Either the reductant or the oxidant can be treated as an analyte. The Ru(bpy)2+3 ECL is used as a detection method for the determination of oxalate and a variety of amine-containing analytes without derivatization in flowing streams such as flow injection and HPLC. When the ECL format is used as a detector for HPLC, unstable post-column reagent addition can often be eliminated and, the problems of both sample dilution and band broadening can be avoided because the Ru(bpy)3+3 species are generated in situ in the reaction/observation flow cell. Since NADH is sensitively detected with the Ru(bpy)2+3 ECL, many clinically important analytes can be detected by coupling them to dehydrogenase enzymes that utilize β-nicotinamide adenine cofactors to convert NAD+ to NADH. Ru(bpy)2+3 -derivatives are used as CL labels for immunoassay and PCR assay with Ru(bpy)2+3/tripropylamine ECL system. The Ru(bpy)2+3 ECL label can be sensitively determined at subpicomolar concentrations, along with an extremely wide dynamic range of greater than six orders of magnitude. Furthermore, it can eliminate disposal and lifetime problems inherent in radio immunoassays. In this paper, basic principles of the Ru(bpy)2+3 ECL are discussed. In addition, analytical applications of the Ru(bpy)2+3 ECL are illustrated with examples.